Mechanical Engineering Principles

190 MECHANICAL ENGINEERING PRINCIPLES

2. What is the potential energy at the top of
   a circle for the motion in a vertical circle?


3. What is the potential energy at the bottom
   of a circle for the motion in a vertical
   circle?


4. What is the potential energy at the ‘mid-
   dle’ of a circle for the motion in a vertical
   circle?

Exercise 84 Multi-choice problems on

motion in a circle (Answers

on page 285)

1. To decrease the horizontal thrust on the
   outer rail of a train going round a bend,
   the outer rail should be:

(a) lowered

(b) raised

(c) kept at the same level as the inner rail

(d) made bigger

2. If the speed of rotation of a conical
   pendulum is increased, the height of the
   pendulum mass will:
   (a) fall (b) become zero
   (c) stay the same (d) rise


3. The minimum tension on the top of a
   vertical circle, for satisfactory motion in
   a circle is:
   (a) zero (b)mg

(c)mv

2

r (d) negative

4. Ifvis the velocity at the ‘middle’ for the
   motion in a circle, the tension is:

(a) zero (b)mv

2

r

(c)mg (d) negative

5. If the tension in the string is zero at the
   top of a circle for the motion in a vertical
   circle, the velocity at the bottom of the
   circle is:
   (a) zero (b)

√

5 gr

(c)

√

gr (d)

√

3 gr